Connecting two figerglass parts?

B

bennecc

New Member
I tried my first ever fiberglass seat build recently. My method was just to make a mold of the seat on the bike then glass over the top of it. I suppose I didn't take enough time in the mold stage, because the fiberglass piece needed a lot of bondo, particularly on one side, to make it look right. So by the time I got it the right shape it was pretty heavy and one side of the cowl was like 1/2" thick.

So, I just glassed a thin layer of cloth over the top of the cowl. After it dried I popped it off and added a layer of mat on the inside. So, I got the same shape but much thinner and lighter. I still need to add at least one more layer to the inside, but before I do I wanted to get some advice about connecting it to an already cured piece.

I was quite happy with the flat part (the seating area) of my original glass piece. So would it be possible to chop the thick bondo cowl off of the original piece and attach the new thin cowl? (obviously I know its possible, but I guess I mean is it a good idea? Will it be a strong bond, if I put a layer or two from the new piece over the top edge of the original piece and over the bottom edge as well? )

Or, should I go get more cloth and resin and just redo the seating area and glass it into the new piece?
 
bennecc said:
I tried my first ever fiberglass seat build recently. My method was just to make a mold of the seat on the bike then glass over the top of it. I suppose I didn't take enough time in the mold stage, because the fiberglass piece needed a lot of bondo, particularly on one side, to make it look right. So by the time I got it the right shape it was pretty heavy and one side of the cowl was like 1/2" thick.

So, I just glassed a thin layer of cloth over the top of the cowl. After it dried I popped it off and added a layer of mat on the inside. So, I got the same shape but much thinner and lighter. I still need to add at least one more layer to the inside, but before I do I wanted to get some advice about connecting it to an already cured piece.

I was quite happy with the flat part (the seating area) of my original glass piece. So would it be possible to chop the thick bondo cowl off of the original piece and attach the new thin cowl? (obviously I know its possible, but I guess I mean is it a good idea? Will it be a strong bond, if I put a layer or two from the new piece over the top edge of the original piece and over the bottom edge as well? )

Or, should I go get more cloth and resin and just redo the seating area and glass it into the new piece?
Click to expand...

What kind of resin are you using? Polyester or epoxy?
 
If using polyester resin, and it has fully cured (read: sat for more than 24 hours) then you need to rough up the surface so the new glass can have something to bite to. 80 grit works well.

Rule of thumb : for every 1 part of thickness, bevel the edges of the glass 8 times that and lay the new glass in the groove.

I.E. 1/8th inch part should have a 1" bevel to lay the new glass into.

Bevel the "bad" side of the part first, then lay your glass in. Trim when green to save yourself some dust.
Flip the part, and grind a new bevel in on the "good" side of the glass that reaches your new glass at the very bottom of your trench. Lay new glass in there.

That way, you have glass that looks like this , where the lined parts are old glass, and the empty part is new glass. Obviously not to scale, and the bevels are much much wider.


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